Common teasel (Dipsacus fullonum L.) has become an aggressive invasive species throughout most of North America, invading roadsides, ditches, rights of way, pastures, and natural areas. This study examined three herbicides used to control common teasel: 1) BK 800, a 2,4-D based broad-leaf herbicide mixed in diesel fuel; 2) Glyphomax® a non-selective glyphosate-based product mixed in water with 5 mL/L of a non-ionic surfactant (Nu-Film®-IR) added; and 3) Transline®, a clopyralid based broad-leaf herbicide used for non-crop areas with 5 mL/L of the Nu-Film®-IR. The herbicides were applied in three concentrations taken directly from the label specifications: the low end, the high end, and the midpoint between the low and high ends. Plant rosette counts taken two weeks after application were compared to counts taken earlier to create a "survival ratio." The majority of the applications resulted in total kill of all common teasel rosettes. Ratios were compared among all treatment groups and the control. All herbicide treatments resulted in significantly (p<0.001) more kills than the control. The different concentrations of each treatment were compared against each other to determine the optimum concentration for common teasel control. The 2 mL/L concentration of Transline®, the 13 mL/L concentration of Glyphomax® and the 55 mL/L of BK 800 were the most effective treatments. There was no significant difference among the efficacies of the three above herbicides. This study provides the first known quantitative study of herbicidal control of common teasel, and it should serve as a starting point for future studies on controlling this invasive plant. / Department of Natural Resources and Environmental Management

MSc., Faculty of Science, University of the Witwatersrand, 2011 / This research investigated the susceptibility of South African indigenous aquatic plants to competition from invasive species, using the competitive interactions of two sets of aquatic plants as a potential indicator. These interactions were studied in two separate experiments: the submersed weeds, Hydrilla verticillata (L.F.) Royle (Hydrocharitaceae) and an indigenous species, Lagarosiphon major (Ridley) Moss (Hydrocharitaceae) and; the floating weeds, Azolla filiculoides Lamarck (Azollaceae) and the indigenous Spirodela polyrhiza (L.) Schleid (Lemnaceae). Plants were grown under differing nutrient levels, and in an addition series of eight different densities, using the reciprocal yield model to estimate competitive ability. The invasive Hydrilla outcompeted Lagarosiphon in terms of mean length, dry mass, and survival. Major algal infestation in the high nutrient level of the Hydrilla/Lagarosiphon experiment altered light and nutrient conditions, which may have played a significant role in the lack of establishment of Lagarosiphon and the poor growth performance of Hydrilla. The invasive Azolla and indigenous Spirodela both performed well in terms of plant mass and increase in number. While Azolla was affected by intraspecific competition, it showed a steady increase in growth and multiplication with an increase in nutrients. The individual mass of Spirodela plants was highest in the low nutrient level, and multiplication rates were greatest in the high nutrient level. Results indicate that the susceptibility of indigenous plants may be increased in highnutrient systems, and that a continuous monitoring programme of aquatic alien species is vital in protecting our indigenous plants from extinction. This research recommends that the method of investigating competitive interactions between alien and indigenous plants be repeated with a variety of aquatic plants, as a means of anticipating susceptibility to invasions.

Common mullein (Verbascum thapsus) is a non-native plant threatening the integrity of natural ecosystems throughout California. Mechanical, chemical, and biological methods have been utilized for control of common mullein. The objective of this study was to determine which of the following treatment cycles is most effective to reduce populations of common mullein at Lava Beds National Monument: annual (once per year), biennial (once every two years), or no treatment. Vegetation type, natural features, site characteristics, and human disturbance were factors considered when analyzing common mullein distribution and abundance. Forty-five pre-existing plots with populations of common mullein were visited during summer 2005. The interrelationship of common mullein with the surrounding high-desert plant communities was assessed by three vegetation sampling methods. Density, cover, and common mullein stages were measured by point-intercept transects, belt transects, and circular macroplots. Simple linear regressions were performed using common mullein density as the dependent variable with multiple independent variables such as shrub, rock, soil, and grass cover. Analysis of variance test showed no significant relationship between density of common mullein and the three treatment cycles (p > 0.05). However, trends observed imply that annual treatment reduces the population of large rosettes and reproductive stalks over no-treatment and biennial treatment. A bivariate correlation test found the circular macroplot to be similar to belt transects for measuring common mullein density (r = 0.84). / Department of Natural Resources and Environmental Management

The Calaveras River is a unique riparian habitat in San Joaquin County, influenced by both tidal water from the San Francisco Bay and impounded rainwater from the New Hogan Dam. The Calaveras River is one of the few river systems in California that does not benefit from snowpack melt. This dynamic system has changed dramatically in both its species composition and hydrodynamic regime due to years of human influences. What was once a thriving population of native plant species has become an environment dominated almost completely by aggressive exotic invasive species. The goal of this project was to remove the nonnative plant habitat by the most cost effective and least labor intensive means. The study area was along a section of river that bisects the University of Pacific campus in Stockton, California. From years of invasive species presence a deep seedbank has developed within the soil which acts to reduce the effectiveness of native plant reintroductions. A technique known as "solarization" was used to eliminate the seedbank and to facilitate the survival of native plants. Tarps were used to eradicate existing plants followed by disturbance of the soil and watering to induce germination of subsoil weed seeds. As the new plant seedlings emerge, tarps are reapplied to eliminate that generation of seedbank plants. After four time series of tarping and watering, a significant difference was found between control plots and treatments utilizing the solarization technique. Treatment 2, which consisted of tarping without weight, was determined to best target the seedbank after four repetitions and resulted in reducing invasive species in the seed bank.

Thesis (DSc)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: No abstract available / AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar

<p>Arundo donax is an invasive species that mostly impacts on sensitive riparian ecosystems. Arundo is also invasive in South Africa, though less is known about its ecology, biology, and impacts. Since California and the Western Cape of South AFrica have similar Mediterranean-type climates, we could assume that the impacts of Arundo on ecosystems in California are likely to be similar in the Western Cape, and that control methods used could be extrapolated for use in South Africa. This thesis attempted to determine what impact Arundo has on biodiversity at the community-ecosystem level.</p>

For decades, South Africa has been heavily infested by invasive alien plants. As a result there is concern over the increasing rate at which the alien plants are replacing indigenous vegetation. Another concern regarding the invasive alien plants is the indirect stress they pose on the environment due to their excessive water consumption. As a result of this, government of South Africa, through the Conservation of Agricultural Resources Acts (43 of 1983) and other environmental legislation, mandates and encourages the removal of invasive alien plants from the landscapes of South Africa. The need for removal of these invasive alien plants led to the formation of the Working for Water Programme (WfW), which is based on a novel approach to environmental management. It contends that the invasion of ecosystems by invasive alien plants could have detrimental effects on water yields from catchment areas, and that employing people to deal with the problem could both protect this vital resource and provide employment and upliftment in poor rural communities. It has been suggested that the supply of information to the public about invasive alien plants is generally poor, to the extent that many people are the causal agents of these plants entering their communities (McNeely 1999). If this lack of awareness is the case, then understanding the drivers of local knowledge which will feed into public awareness is essential to change public perceptions and values surrounding invasive alien plants. It is important to understand local knowledge in order to determine gaps in information transfer and enable them to make decisions that are grounded in local cultural interpretations of place and their environment (Ebohon et al 2000). It is also important to ii understand what the local communities know and what they need to know about these invasive alien plants. This study is premised on developing an understanding of local knowledge and perceptions about invasive alien plants. The assumption is that those involved in the programme would display positive values towards the environment. It is also assumed that those involved in the programme have developed their local/traditional knowledge of invasive alien plants through the educational component of WfW programme. A case study approach of Upper Illovu Working for Water project was adopted. The research was carried out by means of questionnaire interviews. The respondents were drawn from Indaleni community in Richmond, KwaZulu-Natal. Thirty respondents were interviewed and this was inclusive of the field workers, contractors, project manager and people who were not involved in the project but from the same community. Those not involved in the project were used as a control group. Five objectives were utilized to investigate the aim of this study. They were to: a) Determine the respondents’ relationship to, and perceptions of the Upper Illovu WfW project b) Establish the respondents’ understanding and perceptions about the levels of invasive alien plants in the area c) Determine the respondents’ knowledge and perceptions pertaining to prevention of the spread of invasive alien plants iii d) Establish the respondents’ competencies in controlling and managing invasive alien plants and e) Establish the respondents’ perceptions about the project’s ability to deliver on its objectives. The results of this study indicate that most of the respondents were aware of the Upper IIlovu WfW project and its ecological and social upliftment objectives. The pattern of the responses was such that those that did not participate in the project (control group) were for the most part not sure about their responses. Although those who participated in the project displayed better knowledge of issues concerning invasive alien plants, there were many occasions when they failed to provide some responses without being prompted – given clues or examples. To conclude, there was, therefore, a significant knowledge gap about invasive alien plants and information pertaining to them between the two groups. The implications are that those involved with the project must have received some form of information through public awareness about invasive alien plants. That is their traditional knowledge about these invasive plants has been developed by the education from the programme, WfW. But most importantly, the programme remains a key for economic reasons from the perspective of the participants. The need for constant improvement and development of local knowledge regarding these invasive alien plants is important in dealing with their spread and management of their effects on the environment. / Thesis (M.Env.Dev.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

The problems posed by alien invasive plants to our environment and the need for clearing and control has been highlighted by the Working for Water (WFW) programme. Alien plant control requires careful planning, including budgeting. To date, costing and budgeting in alien plant control has largely been a combination of experience on the part of weed 'experts', coupled with much guess work. Weed controllers have through experience calculated the amount of time (or the work rate), recorded as labour days, required for different control actions of different weed habits. These work rates are for weed clearance under ideal conditions and do not take into account the effect of factors such as gradient, access and distance to the weed infestation. Factors affecting the work rate has been researched and modelled by researchers in both alien plant control and the timber industry. While the existing work rate model is useful in its present theoretical state, the model may be improved upon to make it more practical and applicable to the varying conditions of different areas. This research built on existing theoretical research on alien control work rates, and concentrated on two main areas: the adaption and incorporation of the existing research on work rates into a Geographical Information System (GIS), and the creation and demonstration of a Spatial Decision Support System (SDSS) for the management of alien plant control. The eMpofana river in the KwaZulu-Natal midlands was selected as the study area, as there was an existing alien plant control programme. Initially all factors, such as slope, access to weed infestations, terrain and penetrability of infestations, affecting the work rate in the research area were identified. An existing work rate model was then modified to account for the conditions of the research area. Regression analysis was used to derive the relationship between the various factors affecting work rate, creating a work rate model applicable to the study area. Using the results of the regression analysis together with work rate figures adapted from an existing alien plant control programme, a SDSS for alien plant control along the eMpofana River was created. The use of the work rate model and the SDSS in the development of weed control programmes was demonstrated by examining four different management approaches, each having a different management objective . The SDSS provides a spatial component to weed control planning and costing that has thus far not existed. What this research has achieved is the advancement of an alien control work rate model from a theoretical to a more realistic costing process. While some factors affecting work rate may not have been accounted for, the model does address the present inaccuracies in labour costing, and ultimately alien plant control costing. The research has highlighted the disadvantages of GIS in terms of affordability and expertise. The model has wider uses than the eMpofana River, and is the ground work for the further development of a user friendly model applicable throughout South Africa. More effective project budgeting will decrease the likelihood of project failure and this will directly benefit long-term weed control efforts. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

<p>Arundo donax is an invasive species that mostly impacts on sensitive riparian ecosystems. Arundo is also invasive in South Africa, though less is known about its ecology, biology, and impacts. Since California and the Western Cape of South AFrica have similar Mediterranean-type climates, we could assume that the impacts of Arundo on ecosystems in California are likely to be similar in the Western Cape, and that control methods used could be extrapolated for use in South Africa. This thesis attempted to determine what impact Arundo has on biodiversity at the community-ecosystem level.</p>

Torpedograss (Panicum repens) was first observed in Lake Okeechobee in the 1970s and appears to have displaced an estimated 6,400 ha of native plants, such as spikerush (Eleocharis cellulosa), where inundation depths are often less than 50 cm. Two series of studies evaluated substrate exposure and water depth influences on torpedograss establishment and competitiveness. Results revealed that fragments remain buoyant for extended periods and so facilitate dispersal. Once anchored to exposed substrate fragments can readily root and establish. Subsequently, torpedograss thrives when subjected to inundations to 75 cm and survives prolonged exposure to depths greater than 1 m. These findings suggest that fluctuating water levels contribute to torpedograss dispersal and colonization patterns and that low water levels increase marsh area susceptible to invasion. The competition study found that spikerush grown in monoculture produces significantly more biomass when continually inundated to shallow depths (10 to 20 cm) than when subjected to drier conditions (-25 cm) or greater inundations (80 cm). In contrast, torpedograss establishes more readily on exposed substrate (-25 to 0 cm) compared to inundate substrates. During the first growing season biomass production increases as substrate exposure interval increases. However, during the second year, established torpedograss produces more biomass when grown on intermittently wet (0 cm) compared to permanently dry (-25 cm) or intermittently inundated (10 cm) substrates. No difference in production was observed between substrates permanently inundated (10 cm) and any other regime tested. During the first two years of torpedograss invasion, regardless of treatment, spikerush suppresses invasion and torpedograss had little effect on established spikerush, indicating that spikerush-dominated areas are capable of resisting torpedograss invasion. Even so, disturbances that might cause mortality of long hydroperiod species, such as spikerush, may create open gaps in the native vegetation and thus facilitate torpedograss establishment and expansion.